Pre calc help exact value, quadrant II?

How do you solve this??

Find the exact value of the expression given that sec x= -13/12 and

csec y= 5/4, x and y are in quadrant II

1) cos 2x

2) sin 2x

3) tan (x+ y)

1 Answer

Relevance
  • DWRead
    Lv 7
    7 years ago

    sec(x) = -13/12

    cos(x) = -12/13

    sin²(x) = 1 - cos²(x) = 25/169

    sin(x) = √(25/169) = 5/13

    Use double-angle formulas

    cos(2x) = 1 - 2sin²(x)

    sin(2x) = 2sin(x)cos(x)

Still have questions? Get your answers by asking now.